3-2-Apply your critical thinking skills to the accompanying research study descr

Question

3-2-Apply your critical thinking skills to the accompanying research study description. Use the five critical thinking questions provided in the text as a basis for your response.

What am I being asked to believe or accept?
What evidence supports this position?
Are there other ways this evidence could be interpreted?
What other evidence would I need to evaluate these alternatives?
What are the most reasonable conclusions?

A newspaper headline reads “Intellectual pursuits key to preventing Alzheimer’s disease?” The researchers scanned the brains of healthy seniors with no memory loss and asked the seniors to recall how much reading, writing, and game-playing they did when they were growing up. The researchers found that those who reported doing daily brain activities from a young age had very low levels of amyloid plaques, which are associated with Alzheimer’s disease. The study involved fewer than 100 participants and could not account for certain factors that may have confounded the results, including socio-economic factors, diet, and overall health behaviors that might also contribute to amyloid plaque formation and Alzheimer’s risk. It also asked participants, whose average age was 76, to recall how much reading, writing, and game-playing they did when they were in elementary school, high school, and as young adults.

3-3-Explain how Mutation, migration, genetic drift, and natural selection affect evolutionary process. Provide a specific example for each.

3-1 Explain what behavioral geneticists mean by the term heritability and why it is frequently misunderstood. Provide one example of low heritability and one example of high heritability.

Explanation / Answer

Ans 3-1: Heritability is the proportion of this total variation between individuals in a given population due to genetic variation. This number can range from 0 (no genetic contribution) to 1 (all differences on a trait reflect genetic variation). Heritability is the statistical likelihood that variations observed across individuals in a populationare due to genetics. Heritability is presented as a ratio of the amount of variation observedin a population due to genetics relative to the total amount of variation due to both genetic and environmental influences. Heritability is a concept that is frequently misunderstood. Heritability always refers to populations, not to individuals. For example a trait such as shyness is 40% heritable does not say that 40% of one individual’s shyness is produced by genes and the other 60% by the environment.

Taking a height example, if we say that height has 75% variability i.e., 75% of the variation from the shortest to the tallest is due to genes. And it is often misconstrued that X% of our intelligence is due to genes when it is saying that X% of the variation in intelligence across a population is due to genetics.Another example, when considering individuals that are genetically identical or clones and subject to various environments. And when we examine the traits, whatever variation exists cannot be due to the genes since they are identical therefore, the variation is solely affected by the environment. In this case the heritability would be 0.0 or 0%.

Heritability is thus, a proportion that is expressed as a value between 0 and 1. As a result, the heritability numbers that indicate 0.30 or 0.60 or some such proportion to indicate the influence of the genes in the variability of a particular trait. Thus, heritability can be defined as the ratio of variance due to genes to total variance in a population. It is given that genes are responsible for the trait itself. Heritability attempts to establish the influence of nature (genes) versus nurture (environment) on the variability in a population. Therefore, the variation of a trait that has a heritability of .30 can be said to be influenced by genetics at about 30% and the environment at 70%. And heritability is zero if either there is no variation in the genes, whether the result is because of genes going to fixation or because of genetic similarities as in twins or clones.  

Ans 3-2: a: Alzheimer disease can be avoided by brain exercise from the young age.

b: Activities in which the healthy senior people were involved like reading, writing, playing games etc.

c: Yes

d: Genetic studies should be conducted.

e: Alzheimer disease can be avoided by doing brain exercise at the young age.

Ans 3-3: Evolution is the changes in allele frequencies within a single population. Allele frequencies in a population may change due to four fundamental forces of evolution i.e., natural selection, genetic drift, mutations and gene glow. Mutations are the ultimate source of new alleles in a gene pool.

The two important mechanisms of evolutionary change are natural selection and genetic drift. Natural selection usually predominates in large populations whereas genetic drift does so in small ones.

Mutations are the random changes in genetic code and they occur in the sperm and egg cells and are passed so as to become a part of the gene pool, which from there genetic variation may create different versions of mutation. And then the variations that are best suited in the environment are then selected to be carried on into the future generations and then eventually become a dominant trait. For example a mutation may cause parent with gene for bright green coloration to have offspring with a gene for brown colour. It make the gene for brown colour more frequent in the population than they are before the mutation.

Genetic drift is the differences in the reproductive abilities amongst species that happen by chance. In large groups drift does not affect much, but in small groups it can have ahuge impact on the survival rate of that species. Because in the smaller group there are higher chances of certain alleles to be transfered to the next generation. For example, in one generation two brown beetles have four offspring survive to reproduce. While many green beetles were killed when someone stepped on them and had no offspring. Then the next generation would have a few more brown beetles than the previous generation. These changes from generation to generation are known as genetic drift.

Without genetic variation, some of the basic mechanisms of evolutionary change cannot operate. There are three primary sources of genetic variation i.e., mutation, gene flow and genetic drift.

Mutations are changes in the DNA. A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations. Gene flow is any movement of genes from one population to another and is an important source of genetic variation. Sex can introduce new gene combinations into a population. This genetic shuffling is another important source of genetic variation. Genetic drift along with natural selection, mutation, and migration is one of the basic mechanisms of evolution. In each generation some individuals might leave behind a few more descendents than other individuals.

Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift. For example in a beetles population: There is a variation in the traits i.e., some of them are green or brown in colour. And there is a differential reproduction. Environment cannot support unlimited population growth and not all individuals get to reproduce to their full potential. Green beeteals tends to get eaten by girds and are survive to reproduce less often than brown beetles. And the surviving brown beetles have brown offsprings due to their genetic basis. Therefore, all the individuals in the population will be brown.

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